1. Field of the Invention
This invention relates to a composite section for frame members or staves which is composed of a base section, an intermediate section, and a cover section. The cover section, which is solid and bombardment-inhibiting, is provided on its side toward the intermediate section with depressions onto which there engage projections extending from the intermediate section.
2. Prior Art
Such a composite section is known from G No. 86 02 331.4 U1. In the cited reference the base section consists of a box section which is provided on one side with heat insulating stays through which the base section is connected with the intermediate section. To this end, edge strips of heat insulating stays are embedded in grooves of the base section and of the intermediate section, respectively, and are pressed in unreleasably. On the side of the intermediate section away from the base section, an attachment element is screwed on having angularly bent edge strips forming projections which engage in undercut grooves of a cover section made of an aluminum alloy. To apply the cover section, the latter must be slipped on axially in longitudinal direction of the section and must be secured against unintended displacement by additional screws. These safety screws, however, can be screwed in only from the side toward the base section, through the intermediate section, for which reason the width of the intermediate section must be greater than the width of the base section, or else the intermediate section must be laterally offset from the base section in order that the intermediate section protrudes over the base section at least on one side to provide access for insertion of the safety screws.
The design principle of the known composite section has several disadvantages, of which the most important ones are as follows:
In addition to the base section, intermediate section and cover section, it requires for connecting the cover section to the intermediate section at least one attachment element and several fastening and safety screws.
The cover section, made of an especially resistant material, requires a complicated groove cross-section adapted to the angularly bent edge strips of the attachment element, which not only increases the cost of production of the cover section but also reduces the blast resistance thereof over a wide zone.
Lengths of the composite section must have been completed by application of the cover section before frames or staves are formed therefrom, since the cover section cannot be applied subsequently.
The different width dimensions of the base section and of the intermediate section do not permit abutting such composite section at an obtuse angle in corner or crossing regions; instead, they require complicated miter cuts and/or copings of the discrete section parts.
From DE No. 34 04 989 C2 a composite section is known also which consists of a box type base section, an intermediate section formed as an insulating rod, and a solid cover section. In this design, it is true, the application of the cover section does not require additional attachment elements, as the edge of the insulating rod away from the base section is embedded directly in a groove of the cover section and is squeezed therein in the same manner as the opposite edge strip of the insulating rod is embedded and squeezed in a groove of the base section.
A major disadvantage of this design lies in the fact that then the complete composite section must be prefabricated at the factory, since a special rolling tool is required to join the insulating rod, acting as intermediate section, to the base section and to the cover section.